1. Field of the Invention
The present invention relates to permanent bonds in thin components. More particularly, the invention relates to an improved method and apparatus for mounting a permanent stud on a thin substrate by permitting the thin substrate to receive the permanent stud without distorting the flatness of the substrate.
2. Description of Related Art
A number of mechanical and electromechanical assemblies are composed by using studs or pins, such as standoff studs and threaded studs, which emerge from a surface of a substrate or other structure. In such assemblies, standoff studs may be used to separate one element from another or as axles for rotating parts, while threaded studs may be used to fasten one component of the assembly to another. Typically, studs used in manufacturing mechanical or electromechanical assemblies may be attached or fastened to a surface of a substrate by techniques such as crimping, welding, pressing, screwing, or riveting, whereby a hole is first formed in the substrate and subsequently, the stud is inserted into the hole and attached to the substrate by one of the above attaching techniques.
In the prior art, methods of forming mechanical or electromechanical assemblies using standoff studs and threaded studs are typically two sided fastenings. In such methods, a through hole is formed to traverse through the substrate whereby the stud is inserted into the through hole on a first side of the substrate to traverse through the substrate and exit the through hole at a second side of the substrate. The stud is then typically fastened to the substrate at the second end of the substrate using one of the above conventional fastening techniques. In inserting and attaching the stud at only one end of the through hole, the stud is typically pressure-fitted causing an outward force which undesirably bends the substrate to create a non-planar surface of the substrate or forms a retaining ridge around the stud. For example, U.S. Pat. No. 5,579,568 to Hudson et al. discloses a through hole which deforms the stud at one end of the through hole whereby the stud is expanded against the walls of the through hole creating an outward force. The outward force at the one end of the through hole creates an uneven horizontal force which forms a cone like elevation around the inserted stud, thereby causing a non-planar surface of the substrate.
Alternatively, mechanical or electromechanical assemblies may be created using xe2x80x9cdead-endxe2x80x9d holes for standoff stud or threaded stud insertion. In such techniques, the stud is attached, crimped, or the like, at only one side of the substrate using an interference or pressed-in fit to achieve the permanent bond. However, as with through hole techniques, such dead-end hole techniques also cause an undesirable non-planar surface of the substrate. For example, FIG. 1 is a cross-sectional view of a conventional, interference fit or pressed-in stud 2 being inserted by a downward force 4 into a one sided dead-end hole 6 on a substrate 8 to achieve the permanent bond. As shown, the stud 2 is inserted into the dead-end hole 6 by the downward pressure 4 whereby outward forces 12 are created and applied against both the stud 2 and walls of the dead-end hole 6. The outward forces 12 are applied unevenly to one side of the substrate only, thereby radially distorting the stud 2 to force portions of the substrate 8 to elevate around the stud 2 to create a cone effect 14 and undesirably cause a non-planar surface of the substrate 8.
As technology advances, and smaller components are increasing desired in the electronics industry, the studs used in forming mechanical or electromechanical assemblies are increasingly being required to be attached to thinner substrates. The techniques known and used in the art for forming mechanical or electromechanical assemblies, such as those using the conventional studs which create uneven outward forces, cause stress to both the stud and the substrate thereby creating non-planar surfaces of both sides of the substrate. In using thin substrates for modem assemblies, any stress to the thin substrates will cause them to undesirably bend or become distorted. As a result, the prior art techniques are not reliable for controlling the formation of the smaller assemblies as well as maintaining a flat surface of the thinner substrates used in such assemblies. Furthermore, the prior art techniques are time consuming, require several fabrication steps, have increased manufacturing costs, and often require a thick substrate to avoid bending or twisting of the substrate when the studs are inserted into such substrate.
Thus, the prior art techniques of inserting and fastening the conventional studs into substrates are not sufficient for modem mechanical or electromechanical assemblies requiring thin substrates. Therefore further improvements are needed in the art of forming modem assemblies which allow for securing studs evenly into a thin substrate without distorting the flatness of the thin substrate.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide an improved, inexpensive method and apparatus for mounting studs evenly into a thin substrate without distorting the flatness of the surface of the substrate, whereby such method and apparatus allows the location of the stud to be placed within very close positional tolerance limits of less than 0.001 inch.
It is another object of the present invention to provide a method and apparatus for inserting and securing a stud into a substrate in a single operation.
A further object of the invention is to provide an improved method and apparatus for inserting and securing a stud into a thin substrate while maintaining a planar surface of the substrate.
Another object of the invention is to provide an improved method and apparatus for inserting and securing a stud into a shallow dead-end hole while maintaining a planar surface of the substrate.
Still another object of the invention is to provide a method and apparatus for inserting and securing a stud into a substrate which provides improved control of the alignment of the stud.
It is yet another object of the present invention to provide a method and apparatus for inserting and securing a stud into a substrate which fulfills the closest positional tolerances allowing for a flat surface finish.
Another object of the invention is to provide a method and apparatus for an insertion tool for use in the above method and apparatus for mounting studs evenly into a thin substrate without distorting the flatness of the surface of the substrate.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The above and other objects and advantages, which will be apparent to one of skill in the art, are achieved in the present invention which is directed to, in a first aspect, a method of making an assembly component comprising providing a substrate, providing an opening in the substrate, providing a stud having at least one tapered end; and providing a means for positioning the at least one tapered end in the opening in the substrate and securing the stud to the substrate whereby the means applies inward forces to prevent distorting the substrate. The substrate having the stud inserted and secured thereto may then be connected with a second substrate to provide an assembly.
In the preferred embodiment, the thin substrate may comprise an assembly component comprising a lid, cap, heat sink, spreader, or semiconductor having a thickness ranging from about 0.100 inches to about 0.200 inches. The stud having the tapered end is preferably inserted into a blind hole in the substrate and secured thereto the substrate, whereby the blind hole may have a depth ranging from about 0.045 inches to about 0.050 inches.
The stud used in the preferred embodiment preferably comprises a threaded stud or a standoff stud comprising a permanently formable material including metals, plastics, wood, glass, and fiberglass, more preferably the stud comprises stainless steel. The stud preferably further comprises a flank portion and the at least one tapered end of the stud comprises a tapered head portion. The tapered head portion may further comprise knurls thereby providing the tapered head portion with added torque force. In the preferred embodiment, the tapered head portion of the stud comprises an angle of about 15 degrees to about 60 degrees. The angled edges of the tapered head portion of the stud adapt the stud to fit within the opening in the substrate.
The first aspect of the method of making an assembly component further comprises a means for holding the stud, and inserting and securing the tapered end of the stud into the opening in the substrate, or the blind hole in the substrate. The means for holding the stud, and inserting and securing the tapered end of the stud into the opening in the substrate applies inward forces thereby preventing distorting of the substrate. In doing so, the means for holding the stud, and inserting and securing the tapered end of the stud into the opening in the substrate secures the stud to the substrate by moving substrate material inward over the angled edges of the tapered head portion and forms a flange over such angled edges to secure the stud to the substrate.
In the preferred embodiment, the means for holding the stud, and inserting and securing the tapered end of the stud into the opening in the substrate comprises a crimping tool. The crimping tool used in the preferred embodiment is adapted to prevent distorting the substrate by applying the inward forces which cause sidewalls of the opening in the substrate to collapse and form a flange around the angles of the tapered head portion of the stud to secure the stud to the substrate.
In a further aspect, the present invention is directed to a mechanical assembly component comprising a stud having at least one tapered end and a substrate having an opening, preferably a blind hole, on a first side adapted to receive the stud having at least one tapered end, whereby the tapered end of the stud is securely fastened within the opening on the substrate by having a portion of the substrate material moved inward to cover the tapered end of the stud while maintaining a planar surface of the substrate. In such an embodiment, stud having the tapered end secured to the substrate may be connected to a second substrate to provide an assembly.
In the present embodiment, the thin substrate preferably comprises an assembly component comprising a lid, cap, heat sink, spreader, or semiconductor having a thickness ranging from about 0.100 inches to about 0.200 inches. The stud having the tapered end is preferably inserted into the blind hole in the substrate and secured thereto the substrate, whereby the blind hole may have a depth ranging from about 0.045 inches to about 0.050 inches.
The stud of the present assembly preferably comprises a threaded stud or a standoff stud comprising a permanently formable material including metals, plastics, wood, glass, and fiberglass, more preferably the stud comprises stainless steel. The stud preferably further comprises a flank portion and the at least one tapered end of the stud comprises a tapered head portion. The tapered head portion may further comprise knurls thereby providing the tapered head portion with added torque force. In the preferred embodiment, the tapered head portion of the stud comprises an angle of about 15 degrees to about 60 degrees. The angled edges of the tapered head portion of the stud adapt the stud to fit within the opening in the substrate and have a portion of substrate material thereover for securing the stud to the substrate.
In yet another aspect, the present invention is directed to a crimping tool comprising a cylinder having an opening, and an undercut portion and an angled edge on a first end of the cylinder. In the present embodiment, the opening in the cylinder is adapted to receive a stud for insertion into a substrate whereby the undercut portion of said cylinder is adapted to receive the substrate and move substrate material while the angled edge of the cylinder is adapted to receive the substrate material to form a tapered flange over an angled edge of the stud, thereby attaching or securing the stud to the substrate. The crimping tool of the present embodiment is adapted to prevent distorting the substrate by applying inward forces which cause sidewalls of the opening in the substrate to collapse and form a flange around the tapered end of the stud to fasten the stud to the substrate while maintaining a planar surface of the substrate.